Denny Brosh is Maria Ross's partner in the military police, and he's basically defined by his infatuation with her. He's the type to be nosy and lazy, and he takes things personally—criticism sends him spiraling. He and Ross first show up when they're assigned to guard Edward Elric.
In the anime, Brosh gets more active during the rebellion against King Bradley, where he helps save people from execution. The manga takes a different route: after Ross's supposed death, he's devastated, but she decides it's better he doesn't know she survived. She figures he can't keep a secret to save his life. Later, when Roy Mustang launches his coup on Central, Brosh doesn't hesitate to jump into the fighting and lend a hand.
Content compiled by AnimeList.moe from publicly available sources.